If the engine light is on, but no codes are displayed, check it.

When the Check Engine Light comes on your dashboard, it’s an indication that there’s a problem. In most cases, you would get out your code scanner and see what’s causing the fault. So, what do you do when you can’t find any diagnostic codes showing you what the problem is? It is rare but it can be a sign that your Check Engine Light has turned on. However, no codes have been shown. 

If you can’t pull any codes, it’s most likely due to having the wrong scanner or one that is incompatible with your vehicle. The light could be on because of an electrical short, or possibly a blown fuse. You should also consider whether user error, or contamination could be to blame.

This guide will take you through the causes of this uncommon occurrence. This guide will also explain what to do about the rare occurrence. 

What's the purpose of the check engine light?

Otherwise known as Malfunction Indicator Light, the Check Engine Light also goes by the name Malfunction Indicator Light. This indicator lamp is located on the dashboard. It alerts you when there's a problem with the vehicle's engine computer. 

Check Engine Lights are available in various colors, depending upon the manufacturer. This light is usually yellow, orange or amber. If the light comes on solid, there’s an error code that needs to be read. However, if the light is flashing, it’s an indication that something major is happening that requires attention immediately. 

There are two reasons why the engine light is on but no codes

1. Checker for the Wrong Code

Each code scanner is different. You can find plenty of low-cost diagnostic scanners on the market that read the most basic codes, but these aren’t going to give you everything you need with the emissions system or transmission. 

Additionally, if you choose to go to a local auto parts store for a free code scan, the workers there aren’t busting out an expensive diagnostic tool. Instead you will receive a basic scan which may not cover all codes.

There are many good options for scanners: Here's the Best OBD2 Scans

2. Electric Short

It’s unlikely that there’s an electrical short causing your trouble, but not impossible. A short could cause power to jump to the light and force it on.

If this happens, you can verify it by moving the key to the ON position and not starting the engine. It should light up after about a minute. If it doesn’t, a short might be the problem. 

3. User Error

While you may think you have automotive diagnostics in the bag, there’s always the chance that you missed something. Even though the code reader is a simple tool to use, you can’t overlook the possibility that you did something wrong.

Take a moment to re-read the owner’s manual of your scan tool. No matter how easy the instructions may seem, it is important to follow them. It’s possible you overlooked something basic.

RELATED: Check Engine Light – Meaning and Causes

4. Blown Fuse

If the OBD2 scanner has stopped reading codes and is still plugged in, it might be worth throwing out the device. Don’t get rid of it quite yet, because a blown fuse might be to blame.

Just like all other electrical components in your car, the fuse powers the engine control module (ECM), ECU (electronic control unit) and PCM (powertrain control module). The fuse can blow and the necessary component will not be able to get power. The light might come on, even though there’s no actual fault. Read the owner’s manual to figure out which fuses you should check. 

5. Contaminated port

Once you're ready to use your OBD2 scanner you need it to be plugged into the port under your dashboard. If the scanner isn’t working or pulling codes, there could be an issue with the connection itself.

To check if there is any debris or dust in the port, you should examine it. It is usually a quick fix that takes only seconds.

What does an OBDII Code Scanner do?

OBD2 refers to Onboard Diagnostics II. Since 1996, this advanced diagnostics system is included with every car. This technology can be used to diagnose problems in the engine or other systems. 

OBD systems continue to be standard in all new models and makes of cars. With this system, there’s one universal connector used so the device can read a multitude of vehicles. 

OBD2 scanners are essential for reading engine codes if you want to keep track of the vehicle's health. Different code readers can diagnose different systems so you need to choose carefully. 

RELATED : How do I reset a check engine light

How to fix check engine light without codes

Look at your code scanner first. Is the scanner capable of reading many codes? If you haven’t invested in a high-quality scanner, now might be the time. However, it is possible that the scanner may be damaged. Try it out on another vehicle to see if it’s working properly. If not, it’s time to replace it. 

It is also important to examine the location where your plug it in. If there’s debris clogging up the connection, use some compressed air to clean it out. 

The next thing you should do is to look for a blown fuse. The layout of fuses can be found in the owner’s manual. Look for the fuse that’s running the ECU, ECM or PCM and check to see if it’s been blown. The cost of replacing the fuse is minimal and you should be able to get rid of the Check Engine Light.

A professional may be needed for anything beyond the above-mentioned fixes. If you aren’t sure how to hunt down an electrical short, you may want to take it into the shop for further inspection.